The BGS Lexicon of Named Rock Units — Result Details

Loch Laggan Psammite Formation

Computer Code: LLGN Preferred Map Code: LL
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Predominantly micaceous and feldspathic psammite with thin semipelite beds; turbiditic features. Abundant calc-silicate rock lenses and bands. Transitional upper and lower contacts.
Definition of Lower Boundary: Transitional with underlying Coire nan Laogh Semipelite. Base marked by lowest thick (10 m +) grey psammite.
Definition of Upper Boundary: Transitional into overlying Ardair Semipelite - progressive increase in mica content.
Thickness: variable 1.5 - 3.5 km
Geographical Limits: Central and southern Monadhliath Mountains, from Glen Roy to Strath Nairn and eastwards to Aviemore (Speyside).
Parent Unit: Corrieyairack Subgroup (GRCO)
Previous Name(s): Glen Doe Psammite Formation (GDOE)
Alternative Name(s): none recorded or not applicable
Type Area  Loch Lagganside to Glenshirra. Base on south side of upper Spey valley in Coire Bhein. Top on road cuts and sections above Moyonlaggan side. 
Reference Section  South-western flank of Beinn Sgurrach down from top to River Fechlin. 
Reference Section  Shoreside exposures north side of Loch Laggan around Rubha na Magach. 
Key, R M, Clark, G C, May, F, Phillips, E R, Chacksfield, B C and Peacock, J D, 1997. Geology of the Glen Roy district. Memoir of the British Geological Survey, Sheet 63W [Scotland]. 
May, F and Highton, A J, 1997. Geology of the Invermoriston district. Memoir of the British Geological Survey, sheet 73W [Scotland]. 
British Geological Survey, 1995. Glen Roy, Scotland sheet 63W. Solid Geology 1:50000 (Keyworth, Nottingham, British Geological Survey). 
British Geological Survey, 1996. Foyers Scotland Sheet 73E. Solid geology 1:50000 [Keyworth, Nottingham, British Geological Survey]. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S074 S074 S064 S064 S063 S063 S073 S073